Spiral separators are used to separate minerals by providing a descending helical trough down which a mineral slurry flows. A spiral separator can be thought of as a helical sluice. Straight sluices have been used for millennia to recover high-density minerals, most famously gold, from flowing slurries. Records indicate that spiral separators were invented at the end of the 19th century, see for example U.S. Pat. No. 629,595. As the slurry flows down a spiral trough, it is subjected to centrifugal and gravitational forces. The heavier minerals (high-density particles) accumulate toward the inner part of the trough and the lighter minerals (low-density particles) tend toward the outer part of the trough.
Generally, there are three types of product streams from spiral separators and these are commonly termed concentrate, tailings and middlings.
When heavy mineral particles accumulate toward the centre of a spiral they form what is often termed a “concentrate band” rich in heavy mineral.
Spiral separator assemblies can constitute single or multiple helical troughs. Those with multiple troughs are termed “multi-start spirals” in the mineral industry. Common industry nomenclature includes the terms: Single-start, Twin-start, Triple-start and Quad-start, describing spiral assemblies with various numbers of helical troughs.
Conventional spirals are generally arrayed in banks and the slurry is fed to individual spiral troughs, from distributors mounted above the banks, via hoses, pipes and fittings.
An individual trough or helical separating surface will often be referred to in this document as a start.
On a multi-start spiral, multiple troughs are inter-wound on a common axis to increase the feed capacity for a given space. For example, a triple start spiral can treat 3 times as much feed as a single start spiral while occupying an almost identical volumetric space.
It is very uncommon to have more than four starts on a conventional spiral assembly, mainly due to manufacturing and assembly difficulties.
Plastic or aluminium pipes are conventionally utilised as centre columns providing structural support and positional referencing for the troughs in terms of centre, height and spacing.
Spirals are generally assembled by first forming complete, individual troughs. Troughs are then wound together in the case of multi-start spirals and fastened to the column. Other components such as feed boxes, product splitters, product boxes, and repulpers are fitted to complete the assembly.
The invention provides an alternative means of designing, manufacturing, assembling and testing spiral separators.